Field of the Invention and Prior Art
This invention consists of a self propelled machine designed to join sections of pipe made out of thermo plastic materials such a polyethylene together to form a pipeline. Piping of this kind has been used to construct pipelines for the transportation of natural gas, sea water, and other fluids. All kinds of weather conditions may be encountered from extreme heat to extreme cold during the construction process. Pipe used to form these lines ranges in internal diameter size from four to over sixty inches (internal pipe size-IPS) and it comes in various wall thickness (standard dimensional ratio-SDR).
Sections of the pipe are joined together end-to-end either on the surface of the earth or in trenches to form a line. In general, heat is applied to the pipe sections at their ends which permits fusion. A British firm, for example, is reported to use polyethylene socket fittings incorporating electrical resistance heating elements to fuse pipe sections together in a trench. The pipe sections are fitted together at the socket and the heating elements are connected to a source of electricity such as a generator located adjacent to the trench. When energized, the heating elements cause the plastic to melt at the pipe interface such that pipe sections fuse together. The joints are cooled naturally. Labor is required to align and fit pipe sections together end-to-end, hold them in abutting relationship, and to operate the fusion equipment.
Portable fusion equipment has also been used to construct a pipeline. See U.S. Pat. No. 4,342,708 issued Oct. 5, 1982 to Arthur H. McElroy. McElroy Manufacturing, Inc., of Tulsa, Okla., for example, manufactures a fusion machine mounted on wheels like a cart such that it can be dragged by a tractor or other vehicle. The machine is equipped with screw down clamps or jaws which are used to hold a pipe section in juxtaposition with a pipe line and with a device to move the pipe section coaxially with the pipeline to perform the fusion operation. A facing cutter is part of the McElroy equipment and is used to trim the facing ends of the pipe section and the pipeline to make them parallel. A heater plate is carried on the cart such that it may be positioned to apply heat to melt the plastic and form a joint. Like the British apparatus, the cart mounted fusion operation is performed in the open or under tents, haulage equipment is required for the fusion machine, the pipe joints are subject to the elements during the fusion operation, and joint cooling occurs naturally.
The prior art also discloses self propelled machines used for forming metal pipelines, as represented by following:
______________________________________ U.S. Pat. No. Inventor Date ______________________________________ 3,744,259 Wagley July 10, 1973 3,900,146 Fowler August 19, 1975 4,286,914 Davidson, Jr. September 1, 1981 ______________________________________
Wagley, for example, discloses a crawler mounted housing within which sections of metal pipe are supported and welded together to form a pipeline. The Fowler apparatus is similar using a number of housing units connected together to form a train. Both patents indicate that apparatus of the kind disclosed are useful in extreme climates whether cold (such as the artic) or hot (temperatures exceeding 90.degree. F.). Wagley points out that extreme temperatures affect both the efficiency of the workmen and the metalurgical properties of the welds. Davidson discloses means for keeping pipe sections aligned during the pipeline forming process.
Nothwithstanding the state of the prior art, it has been common practice to construct pipelines using sections of polyethylene or poly pipe either by towing or dragging a fusion apparatus such as McElroy's machine in the direction of construction or by using heating elements as discussed above. In either event, the job of constructing the pipe line is both labor and equipment intensive. Generators are required to supply energy to the fusion apparatus and towing means are necessary for hauling it and the generators. Similarly, generators must be towed in the resistance heating unit situation. Lifting apparatus is usually necessary for larger diameter pipe and it too must be hauled or self propelled. In addition, weather conditions including extreme temperatures affect the ability or inability to perform pipeline construction operations. Further, fusion joints are affected by blowing dirt, dust, seeds, rain, and the like which adversely affect their integrity with potential adverse consequential results to the pipeline.